MIL-PRF-81733 Sealing And Coating Compound, Corrosion InhibitiveThis specification covers accelerated, room temperature curing synthetic rubber compounds used in the sealing and coating of metal components on weapons and aircraft systems for protection against corrosion. The Class 1 sealing compound is effective over a continuous operating temperature range of ??65?? to +250?? F \(??54?? to +121?? C\). The Class 2 sealing compound is effective over a continuous operating temperature range of ??80?? to +320?? F \(??62?? to +160?? C\).

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MIL-PRF-81733D

3.3.2.4 Low-temperature flexibility. When tested at temperatures and in accordance with

the method specified in 4.8.10, the cured sealing compound shall withstand the bend test without

cracking, checking, or separating from the panel.

3.3.2.5 Thermal stability. When tested at temperatures and in accordance with the method

specified in 4.8.11, the cured sealing compound shall not blister, crack, or show evidence of

"blowing" at rest or when wrapped 180� on a mandrel. The hardness, after exposure, shall be

within -5 to +15 points of the original "as cured" hardness.

3.3.2.6 Tensile strength (Type II only). The tensile strength of the cured sealing compound

shall be not less than 200 pounds per square inch (psi) for Class 1 or 250 psi for Class 2 (see

4.8.12).

3.3.2.7 Elongation (Type II only). The elongation of the cured sealing compound shall be

not less than 150 percent for Class 1 or 250 percent for Class 2 (see 4.8.12).

3.3.2.8 Peel strength (Types I, II, and IV). When tested as specified in 4.8.13, the peel

strength of the cured sealing compound, as received and after immersion, shall be not less than

15 pounds per inch width (piw) for Class 1 or 20 piw for Class 2. All specimens shall exhibit

100 percent cohesive failure.

3.3.2.9 Anchorage (wet tape test, Type III only). When tested as specified in 4.8.14, the

cured sealing compound shall show no more than a slight widening (1/8 inch) of the scratch.

3.3.2.10 Repairability. The cured sealing compound shall be able to be used for repairing

minor breaks in itself and all other materials qualified to this specification (see 4.3). A second

coat of the sealing compound, applied over a freshly cured coating of the materials specified in

4.8.15, shall show satisfactory bonding with no lifting, blistering, loss of adhesion, or other

coating irregularities. When tested as specified in 4.8.15, the adhesion strength of the compound

shall be not less than 10 piw for Types I, II, and IV; Type III repairability shall be as specified in

3.3.2.9.

3.3.2.11 Air content (Type II only). When tested as specified in 4.8.16, the air content of

the cured sealing compound shall be not greater than 4 percent.

3.3.3 Long-term storage. When tested as specified in 4.8.17, the base compound and curing

agent shall show no hardening, separating, or settling of material after being stored for 9 months.

After the storage period, the mixed sealing compound shall meet the requirements for flow

(3.3.1.4), application life (3.3.1.5), tack-free time (3.3.1.6), and hardness (3.3.2.1).